| 凹陷 | āo xiàn | to cave in; hollow; sunken; depressed | |
| 凹凸HSK 6 | āo tū | concave or convex; bumps and holes; uneven (surface); rugged | |
| 凹版 | āo bǎn | intaglio printing plate (or a print made with it) | |
| 凹镜 | āo jìng | concave mirror | |
| 凹凸不平HSK 6 | āo tū bù píng | uneven (surface); bumpy (road) |